The present invention relates to clamping tools. More precisely the present invention relates to one hand squeeze operated bar clamp tools using wedges to bind a bar.
Squeeze operated clamps are well known. The related art uses an elongated plate to bind a bar at an angle to create a drive or locking action. A familiar application of this method is shown in British Patent 1555455 which shows a caulking gun device. A driving plate 41 and a locking plate 51 are fitted around a shaft. Each plate has a biasing spring also surrounding the shaft.
U.S. Pat. Nos. 4,926,722, 5,009,134 and 5,022,137 are some of a series to J. Sorensen et al covering a squeeze operated bar clamp. A locking plate is positioned in front of a trigger handle. A compression spring surrounds the bar and presses a drive plate forward. The drive plate and drive spring are held in position by the bar. In FIG. 9 of ""134 a locking plate is shown behind the trigger handle.
U.S. Pat. No. 5,005,449 shows a further version of a squeeze actuated clamp in which the trigger handle is parallel to the bar and the handle is squeezed toward the bar.
U.S. Pat. No. 5,161,787 shows in FIG. 3 a shaft driving apparatus. A two speed action is provided through the use of a flexible linkage 90 and a rigid linkage 75. The leverage from handle 34 depends upon the force required of bar 26. The bar moves the opposite direction from the handle motion. Compression spring 38 is surrounded at its non-moving end by ribs of the body structure. The other spring end which presses the drive plate is positioned only by the bar passing within the spring.
U.S. Pat. No. 5,853,168 shows a clamp similar to that of Sorensen except that the clamping jaws point down and the locking plate extends upward directly above the trigger handle. The drive and lock plates are positioned within the housing by a rib 31. The drive plate bias spring 22 is positioned in a similar manner to ""787 above. As seen in FIG. 2 of ""168 the front end of spring 22 is held in position only by bar 12.
U.S. Pat. No. 4,874,155 shows a C-clamp where locking plate release 13 faces rearward. The lock plate spring is positioned around the bar. A drive plate spring is mounted to a shaft separate from the bar. The bar moves in the opposite direction from the handle motion.
In U.S. Pat. Nos. 4,524,650 and 4,739,838, a varying speed lever mechanism for a screwdriver is disclosed. The levers include various sliding and pivoting linkages.
In the clamping devices general design types are seen. One type is a C-clamp where the body of the tool is C shaped. The bar moves oppositely from the trigger handle mounted at the base of body. A caulking gun is also in this category. A second version is a bar clamp where the bar is drawn toward the body in the same direction as the handle is moved. The present invention is directed to the pistol grip bar clamp. In a pistol grip design a part of the housing body extends downward in parallel to a trigger handle such that the handle extends substantially perpendicular to the movable bar. The jaws may be above or below the bar in a pistol grip design. The mechanical limitations and requirements are different between a C clamp and a bar clamp.
The present invention provides several improvements to the function of a one hand squeeze operated bar clamp. The bar and jaw end are both easily removable so that a different length bar can be used with the same tool body. The bar advance action is very fast without loss of clamping force. An easily accessed and intuitive release button is positioned at the side of the tool. The design is comfortable to hold and operate. The drive and lock wedge plates are strengthened by use of a bent channel cross section. A torsion spring is used to bias the drive wedge to allow minimal resistance through a long drive stroke.
The improvements of the present invention may also be of benefit to caulking guns and other such devices.
The bar is entirely separable from the clamp components. A user can easily install a longer bar without the need to purchase another complete clamp. In addition the bar can be pulled out and inserted into the rear; if the jaw end is reversed to face away from the clamp body and attached to the bar behind the body a spreading device is created. An improvement of the invention is that when the bar is removed the internal components will not fall out of position. In particular the drive and lock wedges, and the bias spring do not depend on the bar to hold them in position. In a preferred embodiment the wedges are contained entirely within the body, with the locking wedge linked to a release button or lever. Ribs or notches of the housing body contain the wedges vertically, and the housing walls contain them horizontally. In a preferred embodiment the bias spring is a torsion spring with one spring end pressing behind the drive wedge. The spring coil is supported around a post or feature in the housing. The spring end is therefore also positioned within the housing and does not depend on the bar to be secure. In an alternate embodiment the spring is a compression spring surrounding the bar, where one end is secured within the housing and the other end presses and moves with the drive wedge. The other end of the compression spring may be held by various means in position against the wedge as described later.
A prior art spring is shown in FIG. 3 of U.S. Pat. No. 5,161,787. In this design the spring is secured only at its non-moving end. The ribs surrounding the spring extend well short of drive plates 68. If the spring is to remain stable when the bar is removed the space between the drive plates and the ribs around the fixed end of the spring must be small. The drive stroke must also then be small. If the space is large enough to enable large wedge plate motion and bar speed, then the spring will have a long unsupported end near the plates when the bar is removed. Especially if the tool is bumped or dropped with the bar removed the spring will fall out of position at the plate and it will be difficult to reinstall the bar. Therefore while both U.S. Pat. Nos. 5,161,787 and 5,853,168 disclose methods to hold wedging plates in position with the bar removed, neither provides a reliable solution to-hold the spring.
The drive action of the present invention has a long stroke to enable fast closing. This makes it unnecessary to use a second hand to close the jaw. To maintain a reasonable grip distance the leverage from the handle to close the jaw varies according to the-handle position. In its more extended position the handle provides high leverage and therefore high closing force. As the handle is squeezed rearward the relative speed of the bar increases. In the rear portion of the handle travel a small squeeze motion produces a large bar motion. Both high speed and high force are provided by use of varying leverage with a moving fulcrum. No complex linkages are required. The mechanism operates with low friction.
To make a high speed action practical the device must operate efficiently. Efficiency in this case comprises: low friction, full use of a hand grip distance, and comfortable features and shape.
Another improvement of the invention is the side located release button. The locking wedge is enclosed within the housing and is linked to the user by the release button. The button is accessible by the thumb when the tool is used right handed. All of the fingers on the trigger handle can remain in place as the release is engaged. However the button is also positioned to facilitate left hand use where testing has shown that the middle finger can easily reach back to operate it. Either way this easy access helps when doing fine adjustments where alternate clamping and releasing actions are needed.
Also of importance is the release operation as it is often performed in real applications. Most typically an object is being held to a horizontal surface and the clamp faces downward. With the side release button a user grabs the tool body, squeezes the release button and pulls the tool away. This occurs as one continuous motion.
The prior art releases on the back or top are not convenient for one hand use. Particularly for the pistol grip bar clamp there is no way for the gripping hand to access such releases.
A release lever in front of the handle requires a reduction in usable handle travel in the pistol grip design. The release lever will define the total gripping distance. The trigger handle. that is behind the release lever must then be less than this total gripping distance. This leads to a wasted opportunity when it is desired to have the fastest and easiest possible operation wherein all of a user""s practical grip motion should be used to advance the bar. The distance between the release lever and the trigger handle defines the wasted opportunity of handle motion. Although a small handle motion can be amplified to a large bar motion by appropriate leverage, the faster motion leverage requires higher squeezing effort.
Observation of inexperienced users has indicated another disadvantage to the forwardly positioned release lever. The release lever resembles an operating handle and initial users squeeze the release lever when the intent is actually to advance the bar. After it does not work as expected the user must study the tool to locate the actual trigger handle. In U.S. Pat. No. 5,009,134 FIG. 9 shows an alternate embodiment clamp with a locking lever behind the handle xe2x80x9cwhere preventing inadvertent activation of the braking lever is desiredxe2x80x9d (Col. 5, lines 52-55). However the locking lever of FIG. 9 is not easily accessed. A more intuitive design for the release device is needed.
Another improvement of the present invention is the balance and comfort of holding the tool. The tool body and handle provide surfaces to support the tool on the hand with the hand in a natural position. Especially with the bar extended the handle extension provides support for the cantilevered weight of the handle.